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Using a protractor

Parts of a protractor

A protractor has the following parts.

1. The bottom line of the protractor lines up with one arm of the angle.
2. The centre point of the protractor goes on the vertex (corner) of the angle.
3. An outer scale which starts from zero on the left for measuring angles that swing clockwise.
4. An inner scale which starts from zero on the right and is used for  measuring angles that swing anticlockwise.
5. Degree markings.

Using a protractor

To measure an angle:

1. Place the centre of the protractor exactly on top of the vertex (the corner) of the angle.
2. Place the bottom line of the protractor on the arm of the angle.
3. Decide which scale you will use to measure the angle. You should use the one that starts at zero.
4. Locate where the other arm of the angle crosses the edge of the protractor and read the scale.

In this example the angle measures 32 degrees because it cuts two small marks past 30 on the inside scale.

Exercises

Calculate the angle between the two lines using a protractor.

Level 1

1

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2

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3

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4

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5

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6

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Level 2

1

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2

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4

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5

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6

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Check your answers